A liquid containing microscopic air bubbles, which are called microbubbles, having a diameter of 0.5 mm or less has heretofore been used in different fields, and various devices for generating microbubbles in a liquid have been proposed. The microbubble generating device comprises a mixer provided with a venturi tube. In the mixer, a gas is drawn in downstream of the throat part of the venturi tube to generate air bubbles, and the liquid and the air bubbles are delivered through a pipeline connected downstream of the mixer to a redistributor while the air bubbles are dissolved in the liquid. The venturi tube of the redistributor accelerates the liquid and air bubbles again, and a jet flow with which microbubbles are mixed is injected from a nozzle tip provided downstream of the redistributor.